Related Stories

DNA barcoding Crushing insects into a 'soup' offers scientists a quick and accurate way to monitor the biodiversity of an area, say Australian researchers.

In the past, scientists have spent thousands of hours collecting, classifying and recording insects in order to understand which animals live in an area. Testing for any change in their abundance required them to undertake the same process all over again.

The new technique, known as metabarcoding, uses short sequences of DNA to identify different species from a sample that includes hundreds of different animals.

Ecologist Roger Kitching and colleagues from Griffith University, took part in an international study that compared the results of metabarcoding analysis with traditional insect identification techniques.

Samples were collected from tropical rainforest in Malaysia's Danum Valley, subtropical rainforest in Ailaoshan, China and temperate woodland in the UK.

The insect collections, totalling 55,813 specimens were each divided in half, with one half painstakingly analysed using traditional techniques -- a task involving 2,505 hours of effort by taxonomic experts.

The other half of each group was crushed into an insect 'soup' and the soup's molecular signals analysed using a high throughput DNA sequencer.

"Every living organism contains DNA, and even small fragments of that DNA can be extracted and used to identify species," says Kitching.

The results, reported in Ecology Letters, demonstrated a very high level of correlation between the two sets of data.

"While metabarcoding has been used previously, this was the first time it had ever been done in parallel with a traditional biodiversity assessment," explains Kitching.

"It showed that if you are interested in estimating how many species are present in an area, this technique is fast, accurate and requires much less expertise."

"But if you want to understand the ecology of an area, you will still need to use the traditional approach."

Conservation implications

Logically, Kitching says, the technique could be applied to any mass of data; in fact metabarcoding has already been used to monitor the abundance of endangered species in Vietnamese and Laotian forests.

There, scientists from WWF and Copenhagen University analysed a soup made from bloodsucking leeches to build a list of the mammals present in the area, and from that determine whether conservation efforts were working.

As the process is rapid and relatively inexpensive, it can be repeated regularly, giving researchers quick insight into whether the biodiversity of an area is changing, says Kitchling.

"If the environment changes for the better or for the worse, we will know about it because the mix of DNA present in the 'insect soup' will also change.

Surprising results

While metabarcoding proved its value during the study, there were still a few surprises, Kitching says.

"Our insect sample came from China," he explains. "We were interested in moth diversity so used light traps to catch them."

But when the collection was analysed the researchers found not only insect DNA, but also the molecular signatures of three partridges.

"We were a bit puzzled about how we had ended up with bird DNA in our insect sample until we realised that in addition to moths, we had caught mosquitoes and blood-sucking flies.